A conventional fastening device for tighten a string or shoe lace is shown in FIGS. 8 and 9 and generally includes a case 60 composed of a base 61 and a cover 62 between which a space 63 is defined and a ratchet device, a gear set 70 and a reel 80 are received in the space 63. A shaft 64 extends through the case 60, the ratchet device, the gear set 70 and the reel 80, and is connected to a knob 65 which is rotated relative to the case 60 so as to rotate the ratchet device which drives the gear set 70 and the reel 80. Two ends of a string 81 are fixed on the reel 80 and the string 81 is reeled around the reel 80. The ratchet device includes a ratchet wheel 71 and a pawl 66 is pivotably connected to the cover 62 and is cooperated with a torsion spring 661 so that the pawl 66 is normally biased by the torsion spring 661 toward the ratchet wheel 71. The ratchet wheel 71 has ratchet teeth which are shaped so that the ratchet wheel 71 is allowed to rotate counter clockwise and cannot rotate clockwise because of the pawl 66. The pawl 66 includes a protrusion 662 extending from an end thereof and a shifting lever 67 pivotably or movably connected to the cover 62, the shifting lever 67 includes a pushing end 671 which pushes the protrusion 662 away from the ratchet wheel 71 by operating the shifting lever 67 exposed on an outside of the cover 62. When the user rotates the knob 65 counter clockwise, the gear set 70 is driven by the ratchet wheel 71 and the reel 80 is rotated at higher speed because of the ratio of the gear set 70 so that the string 81 is securely reeled on the reel 80 and the object that the string 81 ties is secured. When shifting the shifting lever 67, the pawl 66 is pivoted and away from the ratchet wheel 71. The string 81 is then able to be loosened manually.
However, there are too many parts in the fastening device which has a limited space to receive all the parts, so that it is difficult and takes a lot of time to assemble the fastening device. Besides, the exposed shifting lever might tangle foreign objects, especially when the fastening device is installed on shoes.
The present invention intends to provide a fastening device that includes a clutch device which is activated simply by operating the knob upward or downward, and the knob is positioned in each of the two positions.